Olefin polymers, being excellent in processability, chemical resistance, electrical properties, mechanical properties, and the like, are processed to extrusion molded articles, injection molded articles, hollow articles, films, sheets, fibers, and the like, and are used in many applications including daily goods, kitchenware, packaging films, nonwoven fabrics, household electrical appliances, mechanical parts, electrical parts, and automotive parts.
In particular, olefin polymers comprising 4-methyl-1-pentene are used in various fields including food, medical treatment, electronic information, household electrical appliances, experimental equipment and stationery, as a resin being excellent in lightness, transparency, gas permeability, chemical resistance, and furthermore heat resistance.
These olefin polymers are generally produced using a catalyst comprising a transition metal compound and an organoaluminum compound, i.e., so-called Ziegler catalyst.
Patent Document 1 proposes a 4-methyl-1-pentene random copolymer, and a composition containing the copolymer.
However, the copolymer in this document has multiple reaction sites, thus having a drawback of involving the easy generation of a low stereoregularity polymer or a low-molecular weight polymer. These polymers cause an adverse influence as a sticky component during film formation. Further, the copolymer in this document involves the bleeding-out of the low-molecular weight component to the surface, and has decreased mechanical properties such as toughness and strength. The improvement as a product is thus needed.
On the other hand, olefin polymers obtained using an organometallic complex catalyst containing a cyclopentadienyl group are generally characterized by the polymers having a uniform composition in terms of e.g., the molecular weight, but it is pointed out that these polymers are inferior in heat resistance as compared with polymers obtained using conventional Ziegler catalysts. The reason is said to be attributable to the heterogeneous bond of monomer units contained in several percentage in the olefin polymers produced using usual metallocene catalysts, resulting in adverse influence in physical properties.
Patent Document 2 proposes a 4-methyl-1-pentene polymer having excellent heat resistance and a high molecular weight with a narrow molecular weight distribution. However, the polymers obtained therein still need to be improved in terms of heat resistance, toughness, and molding processability.
Poly(4-methyl-1-pentene) is excellent in releasability. Poly(4-methyl-1-pentene), because of its lower surface tension as compared with other resins, exhibits excellent releasability during molding operation, i.e., poor compatibility with other resins. As a result, the use of other resins as a modifier to modify poly(4-methyl-1-pentene) in terms of e.g., toughness, impact properties results in the failure to exhibit these properties. Patent Document 3 and Patent Document 4 deal with this problem by proposing the use of 4-methyl-1-pentene polymer compositions. However, these compositions need to be further improved in terms of toughness, impact resistance, and transparency.
Meanwhile, vibration dampers are widely used to prevent or dampen vibration caused by device components and then reduce the vibration to an appropriate level. The vibration dampers are used also as a material having specific vibration damping properties to provide a high quality sound in a speaker and the like of audio devices.
As a polymer material having vibration damping properties, conventional art provides a material having a large peak value of loss coefficient tan δ, as obtained by measuring a dynamic viscoelasticity thereof, the loss tangent tan δ being an indicator of vibration damping properties of the polymer material. Examples of the material include styrene/isoprene/styrene block copolymer (SIS) and hydrogenated products thereof.
SIS, having a large peak of loss tangent tan δ at around a room temperature, has excellent vibration damping properties at around a room temperature. However, SIS, because of having a sharp peak of tan δ, has inferior vibration damping properties at a temperature that is not around a room temperature. Meanwhile, the hydrogenated SIS, which is produced through a two-stage process of polymerization and hydrogenation, costs high for its production; and thus, an industrial application thereof is limited.
A rubber vibration damper has excellent properties in its performance, but is difficult to form so as to have an arbitrary shape in its practical use. Polypropylene and 4-methyl-1-pentene homopolymer have their tan δ peaks at around a room temperature. The peak values, however, are small, and this leads to a problem such as low size precision during molding operation. A polyvinyl chloride (PVC) vibration damper possibly has an adverse influence on environment by, e.g., emitting harmful gas during burning.
For these reasons, there has been desired a material excellent in lightness, flexibility, stress absorption, stress relaxation, vibration damping properties, toughness, scratch resistance, abrasion resistance, and mechanical properties, having no stickiness during molding operation and being excellent in the balance among these properties.